Many computing systems comprise multiple electrical devices coupled together. Examples of such devices include computers (e.g., servers), switches, etc. Many data centers include hundreds or thousands of computers, switches, etc. coupled together in multiple equipment racks.
Electrically coupling such devices together can be a huge undertaking in and of itself. Electrical cables can be used to connect the devices together but can result in a mass of cables that should be individually tagged and identified. Cables also have a substantial cost and weight to the equipment racks in which the devices typically reside.
Another choice for interconnecting electrical devices (computers, switches, etc.) besides cables, is the use of a “backplane.” A backplane comprises a printed circuit board (PCB) containing conductive traces and connectors. The various electrical devices have corresponding connectors. As an electrical device is installed, the electrical device's connector mates to the backplane's connector thereby electrically coupling the electrical device to the backplane. The traces on the backplane couple the electrical devices together as desired.
While backplanes reduce or eliminate the need for cables, the use of backplanes unfortunately reduces flexibility in terms of where the devices can be installed. In some situations, it is possible that certain types of electrical devices should not be connected together. For example, connecting certain devices may result in a transmitter of one device undesirably being electrically coupled to a transmitter of the other device, rather than a receiver. Using cables as the connectivity medium, the devices can be installed virtually anywhere and a technician simply connects the cables to where ever the devices are installed. The use of cables generally precludes device mismatches from occurring. If a backplane is used in a rack as the connectivity mechanism among devices, it may be necessary to dedicate certain slots in the rack to ensure that device connectivity errors do not occur. Dedicating slots in a rack for a specific use reduces the flexibility of a user to install electrical devices as he or she would otherwise desire.
Another problem is characteristic of electrical devices whose configuration can be changed. To change the configuration of a server that is currently in an “off” state, such a server would typically have to be booted up (initialized) for the purpose of changing the configuration. Many configuration settings, however, are only implemented during the boot process. Thus, a computer whose configuration settings have just been changed must be re-booted for the new configuration settings to take effect. Such computers, therefore, must be booted twice—once to change one or more configuration settings and a second time to cause the new settings to be implemented.